This invention relates generally a surgical instrument and, more particularly, to a forceps instrument which may be used in arthroscopic surgical procedures involving the knee, the shoulder, and other joints.
Arthroscopic surgery of the knee, the shoulder, and other joints is a commonly accepted surgical procedure. A number of instruments have been developed for such surgeries, including those shown in U.S. Pat. Nos. 4,662,371 and 4,944,093. Instruments such as those shown in these patents are typically used with an arthroscope which allows the surgeon to view the interior of the joint through an eye piece or, alternatively, on a video display screen.
Efficient arthroscopic triangulation generally requires wide separation of the viewing instrument and the operating instrument. Normally, this is not a problem and has been made easier by the use of optical devices having angled fields of view, as well as by the use of curved operating instruments. However, on frequent occasions involving certain joint locations, such as the anterior horn of the lateral meniscus in the knee and the inner edge of the anterior glenoid labrum in the shoulder, effective triangulation is difficult. In these locations, the optimum viewing portal is often the best portal for the operating instrument.
A basket forceps is often used to remove tissue associated with tears of the lateral meniscus in the knee and the anterior glenoid labrum in the shoulder. The conventional design is a forward cutting instrument which may slice through or nibble off a portion of the torn tissue. A basket forceps cuts most efficiently when the tissue to be cut is approached directly with an open instrument jaw. For tears in the posterior portion of the lateral meniscus, for instance, conventional instruments work well when entering the knee joint from an anterior medial or anterior lateral portal. However, torn tissue in the anterior horn of the lateral meniscus cannot be easily approached with a forward cutting device. The surgeon must either work awkwardly with a forward cutting basket forceps or create an instrument portal close to the viewing portal, which makes triangulation awkward and difficult. These difficulties increase operating time and surgeon frustration.
An object of the present invention is to provide a surgical instrument which has an instrument jaw which opens in a generally backward-facing direction (i.e., in a direction which faces the instrument shaft and handle) to facilitate the cutting of body tissue in certain joint locations.
Another object of the present invention is to provide a surgical instrument in which the cutting plane of the instrument is laterally adjacent (or offset from) the longitudinal axis of the instrument support shaft to maintain a narrow instrument profile and to facilitate passage of the instrument through the operating portal.
Yet another object of the present invention is to provide a surgical instrument which is especially well-suited for surgical procedures involving the anterior horn of the lateral meniscus of the knee, the inner edge of the anterior glenoid labrum in the shoulder, and other particular joint locations.
These and other objects of the invention are achieved in a surgical instrument for cutting body tissue which comprises an axially elongate support shaft, a tip assembly permanently attached to the distal end of the shaft, and means extending coaxially with the elongate support shaft for actuating the instrument. The tip assembly comprises a stationary portion and a movable portion having respective tissue cutting edges which define a cutting jaw which opens toward the elongate support shaft. The cutting jaw is laterally offset from the longitudinal axis of the shaft. The means for actuating the instrument comprises means for applying a closing force and an opening force to the movable portion of the cutting jaw.
In a preferred embodiment of the invention, the stationary portion of the tip assembly is permanently attached to the distal end of the support shaft, and the movable portion of the tip assembly is pivotally attached to a distal end of the stationary portion. The stationary portion of the tip assembly comprises a plurality of cutting edges which define an opening in the stationary portion which extends axially adjacent a longitudinal axis of the support shaft. The movable portion of the tip assembly comprises a cutting element having a plurality of cutting edges which cooperate with the cutting edges of the stationary portion to define the cutting jaw.
The cutting jaw has a fully open position in which the cutting element extends outwardly from the longitudinal axis and toward a proximal end of the elongate shaft at an angle of approximately 60.degree.. The cutting jaw has a fully closed position in which the cutting element is disposed within the opening in the stationary portion of the tip assembly. The tip assembly has an overall height dimension, when the cutting element is in the fully closed position, which is substantially equal to a corresponding cross-sectional dimension of the elongate support shaft.
In the preferred embodiment of the invention disclosed, the means extending coaxially with the elongate support shaft for applying a closing force and an opening force to the movable portion of the cutting jaw comprises a wire rod. A distal end of the wire rod is flattened and pivotally attached to the moving portion of the tip assembly.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.